This invention relates to an attachment for groundworking and material handling machines, and more particularly to an attachment operable for performing various work functions. The invention further contemplates a novel strut assembly for such an attachment.
In many groundworking and material handling machines, there generally is provided a mobile support frame mounted on wheels or track units, a rotatable platform mounted on the support frame on which there is provided an operator""s station and a boom mounted on the platform and angularly displaceable about a horizontal axis. Typically, the front end of the machine further is provided with a handle or dipper stick pivotally connected to the free end of the boom and some form of groundworking or material handling assembly mounted on the free end of the handle or dipper stick. Such assemblies typically consist of an excavator bucket, a rake, a pair of jaws such as in a grapple or sets of shears or crushers and the like. In most of such constructions, the boom, handle or dipper stick and the assembly mounted on the handle or dipper stick are pivoted by hydraulic cylinder assemblies. In some applications, where the working assembly consists of a pair of jaws, it is common to provide for the pivotal movement of both jaws, the pivotal movement of only one jaw and the fixed positioning of the other jaw or the pivotal movement of one jaw and the fixed positioning of the other jaw but the angular adjustment of the position of the fixed jaw.
In one common attachment for machines of the type described, there is provided at least a lower jaw member sometimes referred to as a xe2x80x9cthumbxe2x80x9d pivotally connected to the underside of the handle of the machine, a hydraulic cylinder assembly operatively interconnecting the underside of the handle and the lower jaw member for angularly displacing the lower jaw member relative to the handle, and often an upper jaw member in the form of a bucket, grapple jaw, shear blade, rock crushing jaw, rake 100 or the like, pivotally connected to the handle, in which the lower fixed jaw member may be used independently of or in cooperation with the upper jaw to perform various work functions.
In the type of attachment described, in adjusting the angle of the lower jaw member relative to the handle, it has been the common practice in the prior art simply to operate certain controls at the operator""s station on the machine to supply and withdraw fluid to and from opposite ends of the cylinder assembly interconnecting the handle of the machine and the lower jaw member to extend or retract the rod portion thereof, correspondingly adjusting the angle of the lower jaw member, and then blocking the flow of fluid to and from the opposite ends of the cylinder assembly to lock the rod portion thereof and thus provide a strut of a fixed length.
Such type of arrangement, however, is relatively costly to manufacture in that it requires running fluid supply and return lines from the platform of the machine along the boom and handle to the cylinder assembly for the lower jaw member. Such fluid supply and return lines and the various fittings required add considerably to the cost of such attachments. Furthermore, such lines are vulnerable to damage and require periodic maintenance.
It thus has been found to be desirable to provide the type of attachment as described which not only provides for an expeditious angular adjustment of the lower jaw member and a rigid strut therefor for withstanding substantial loads imposed thereon in performing various work functions but further an avoidance of the relatively high manufacturing costs and potential maintenance problems inherent in comparable prior art attachments.
The present invention provides an improvement over comparable attachments in providing an attachment connectable to a boom of a machine such as a groundworking machine or a material handling machine generally comprising a handle pivotally connectable to the boom of the machine, an arm member pivotally connected to the handle and an extendable strut interconnecting the handle and the arm member consisting of a hydraulic cylinder assembly having a cylinder member pivotally connected to the underside of the handle and a rod member pivotally connected to the arm member. The strut further includes means intercommunicating the base and rod ends of the cylinder member, at least one electrically operated valve disposed in such intercommunicating means and operatively connectable to control means provided at the operator""s station on the machine, selectively operable to open such valve and thus permit the free flow of fluid between the base and rod ends of the cylinder member, and correspondingly the angular displacement of the arm member relative to the handle upon maneuvering the front end of the machine by the operator, and close such valve and thus preclude the free flow of fluid between the base and rod ends of the cylinder member, and correspondingly the setting of the angular relationship of the arm member relative to the handle, and an accumulator selectively communicable with the variable volume chambers of the cylinder member for compensating for the fluid volume requirements of such chambers.